1) Field of the Invention
This invention relates to a light-cured, fluoride-releasing, dental restoration composition effective for filling cavities and bonding composite resin or amalgam to teeth and to achieve a strong bond and reduced marginal microleakage.
2) Description of Prior Art
Amalgam is an exceedingly common product used in filling tooth cavities in human beings. The main constituents of amalgam are mercury and silver. Amalgam had problems because good adhesion between the tooth and the amalgam is not obtained and also a good seal between the amalgam and the tooth is not obtained which substantially prevents ingress of mouth fluids and bacteria into the filled cavity (microleakage) and thus prevents further decay of the teeth. Thus, marginal microleakage has been an inherent problem in conjunction with amalgam restorations. Amalgam also requires cavity preparations plus usage of a retention form which can cause damage to non-carious tooth structure.
It is becoming apparent that a goodly number of individuals are allergic to mercury and are not able to utilize amalgam in their teeth. It has long been known that there is a need for a dental restoration composition which does not include mercury. It has been known to construct dental restoration compositions of a resin composition such as is shown and described in U.S. Pat. No. 4,500,657, inventor Narayang Kumar. A similar composition is discussed within U.S. Pat. No. 4,814,362. Improvements in dental adhesives are discussed in detail within U.S. Pat. Nos. 4,479,782 and 4,657,941. These adhesives are commonly used as cement liners to stop microleakage under restorations. The bonding agent with the cement liner is to adhere to the dentin and reduce pulpal irritation.
Recently, four in number of fluoride-releasing liners have been introduced in the market. These four are sold under the tradenames of TIME LINE, VITRABOND, XR IONOMER and ZIONOMER. These four liners have been developed to overcome the major disadvantage of conventional lining cements which were (1) long-setting time (three to five minutes), (2) surface dissolution upon acid etching, (3) dehydration upon drying of etched enamel and (4) low mechanical strength. These four liners have achieved some success with (1), (2) and (3), but with (4) only limited success has been obtained. Actually, the mechanical strength of these liners is just not adequate for longevity of the restoration utilizing the liners.
Some lining cements require the removal of a dentin smear layer prior to usage. The smear layer is a naturally produced layer during the preparation of the tooth cavity which functions as a natural cavity liner. It has been thought by some that this layer must be removed for optimum bonding. The removal of this dentin smear layer generally increases hypersensitivity.